A folded or buckled composite structure can be produced by attaching a continuous fibrous layer to a continuous shrinkable layer at discrete points. The attachments can be achieved by intermittent thermal, ultrasonic or adhesive bonds, and by mechanical or hydraulic needling. As disclosed in commonly owned, co-pending patent application entitled “Textile Laminate Having Pile-Like Surface,” bearing Ser. No. 10/455,594 and filed on Jun. 5, 2003, by the same inventor as the present invention, intermittently bonded and subsequently gathered or folded fibrous products that present upstanding loops or buckled fibers on their surface simulate the “loop pile” of floor coverings. This commonly owned, co-pending patent application is incorporated herein by reference in its entirety. These textured products offer features and advantages including dust, dirt, and liquid penetration resistance combined with resilience against “matting” or collapsing of pile under the heavy load-reload of heavy traffic. In one embodiment, the height of the loops is about 2 mm and the loops are spaced about 2 mm apart, matching conventional pile carpets. The relatively large height and spacing produce substantial anchoring bonds and leave sufficient distance between bonds to buckle the relatively heavy yarns or fabrics forming the buckled “pile.”
Also, as discussed in this commonly owned, co-pending patent application, the inventor has discovered that fibrous structures consisting of shallower and denser loops of fibers buckled or bent with a higher frequency provide improved resistance to “matting” or crushing under heavy repetitive loading that can occur on flooring, upholstery or wall covering, provided that the buckled or looped fibers descend into a layer of adhesive within a length of less than about 2 mm. The final product is dimensionally stable and resists planar deformation.
A folded or buckled composite structure can also be produced by stitch-bonding a continuous fibrous layer with shrinkable yarns at discrete points. Stitch-bonding of shrinkable yarns to non-shrinkable or less shrinkable fibrous layers in order to produce denser, shorter and more frequent buckled loops, offers several advantages. The first advantage is that the attachment points are perforations, which soften rather than harden the stitched fibrous substrate, thereby making it more amenable to gather and bulk. The second advantage is that, unlike intermittent bonding, the attachment frequency can increase by using smaller needles, spacings (higher gauges) and smaller stitch spacings (higher CPI). With intermittent bonding, space should be provided for the bonds, and to make the bonds stronger the space taken by the bonds must be relatively large. The third advantage with stitch-bonding is that a large variety of yarns and shrinkable fibrous layers can be used. For example, non-shrinkable or shrinkable yarns can be used to attach a fibrous layer to an elastic, tensioned shrinkable substrate, as illustrated for example in U.S. Pat. No. 4,891,957, or tensioned elastic yarns can be used to shrink and bulk a fibrous substrate, as illustrated in U.S. Pat. Nos. 4,704,321 and 4,773,238. In addition heat-shrinkable partially oriented yarns (POY) can be attached to a fibrous substrate, as illustrated for example in U.S. Pat. Nos. 5,707,710, 5,879,779 and 6,407,018. In addition to gathering the fibrous substrate, the network of stitching yarns also reinforces the gathered product.
For use as floor or wall coverings, the stitch-bonded and gathered products known heretofore, however, require adhesives or binders at least on the upper strata to anchor the bulked layers. To obviate the need for adhesives or binders in the upper strata, the dimensional stability of the conventional stitch-bonded and gathered products needs to improve. The instability of the conventional products originates from the elasticity or the instability of the shrunk stitch-bonded yarn system, or the elasticity or the instability of the stitched substrate. Even products that are stitched with partially oriented yarns (POY) and subsequently gathered and heat set could not be fully stabilized without some distortion, because the slack in the stitching system can not be completely removed by tentering without removing at least some of the gather. The conventional products typically require additional treatment with binders or resins to improve their dimensional stability. Molded or embossed versions of the conventional stitch-bonded fabrics tend to be deformable and lose their shape, unless encased in resin concentrations or co-molded or co-embossed with stiff backings. However, resin treatment sufficient to stabilize these products also gives the surface of the product a firm or harsh non-fabric-like hand, while stiff backings produce inflexibly stiff products.
Additionally, the conventional stitch-bonded gathered products aimed for uses that require crush-resistance need an adhesive layer sufficiently heavy to encase the lower strata of the buckled loops, up to a uniform and well-controlled height, while leaving the upper strata free of adhesive binder in order to preserve the soft textile feel at the surface. Low-viscosity thermoset binders suitable for this purpose tend to seep upward towards the surface of such products, while suitable thermoplastic-binders introduced from the backside require heat and pressure that tend to flatten the structure. Introducing a layer of thermoplastic binder as a co-substrate along with the fibrous layer would cause the binder layer to buckle as well and follow the contour of the buckled fibrous layer, failing to concentrate near the bottom within the lower strata. The need of locating a planar adhesive (binder) layer in the lower strata is even more important when the product is laminated to a backing layer. A planar adhesive layer located in the lower strata can be preheated and pre-activated before lamination, thus minimizing the time and pressure needed to laminate, and, in turn, minimizing the flattening effect of the lamination.
Therefore the need exists for stitch-bonded products that have improved dimensional stability.